Jayant Tilekar - Academia.edu (original) (raw)

Papers by Jayant Tilekar

Research paper thumbnail of Chiron approaches to polyhydroxylated piperidines: promising glycosidase inhibitors

Arkivoc, Jul 14, 2002

New chiron approaches towards the syntheses of polyhydroxylated piperidine analogues are describe... more New chiron approaches towards the syntheses of polyhydroxylated piperidine analogues are described. The methodologies involve 1,3-addition of methyl magnesium bromide and silyl ketene acetal to D-glucose derived nitrone, intramolecular Michael addition to D-glucose derived α,β-unsaturated ester and double reductive amination of 5-keto aldose as key steps.

Research paper thumbnail of Chiron approaches to glycosidase inhibitor azepanes and c1_c6 segment of carbonolide b_aglycone of carbomycin b

Research paper thumbnail of Plasmid encoding IAA and a method thereof

Research paper thumbnail of An Expeditious Synthesis of a (3S,4S,5R)-Trihydroxyazepane

Tetrahedron Letters, Dec 30, 2003

Multi-membered N-heterocycles Multi-membered N-heterocycles R 0690 An Expeditious Synthesis of a ... more Multi-membered N-heterocycles Multi-membered N-heterocycles R 0690 An Expeditious Synthesis of a (3S,4S,5R)-Trihydroxyazepane.-Starting from the optically active (I) derived from D-glucose a practical synthesis for the title compound (VIII) is presented. This approach is also useful on a multigram scale.-(DHAVALE*,

Research paper thumbnail of Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar a-Diazo Ketones

Synthesis Stuttgart, 2000

paper, Synthesis 2000; 2000(3): 395-398 DOI: 10.1055/s-2000-6343. © Georg Thieme Verlag, Rüdigers... more paper, Synthesis 2000; 2000(3): 395-398 DOI: 10.1055/s-2000-6343. © Georg Thieme Verlag, Rüdigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. This journal, including all individual contributions and illustrations published ...

Research paper thumbnail of A short and efficient synthesis of 1-deoxy-castanospermine and 1-deoxy-8a- epi-castanospermine

Tetrahedron Letters, Jan 22, 2001

A new route for the synthesis of 1-deoxy-castanospermine 2 and 1-deoxy-8a-epi-castanospermine 3 h... more A new route for the synthesis of 1-deoxy-castanospermine 2 and 1-deoxy-8a-epi-castanospermine 3 has been developed via a sequential triple reductive amination process of a suitably protected d-gluco-oct-5-ulo-1,8-dialdose, which was easily prepared by three carbon homologation of readily available α-d-xylo-pentodialdose using an appropriate Grignard reagent followed by oxidation.

Research paper thumbnail of Intermolecular Michael Addition of Substituted Amines to a Sugar-Derived α,β-Unsaturated Ester: Synthesis of 1-Deoxy- d - g luco - and - l - i do -homonojirimycin, 1-Deoxy-castanospermine and 1-Deoxy-8a- epi -castanospermine

The Journal of Organic Chemistry, Feb 1, 2001

The synthesis of polyhydroxylated piperidine alkaloids, namely, 1-deoxy-D-gluco-homonojirimycin 3... more The synthesis of polyhydroxylated piperidine alkaloids, namely, 1-deoxy-D-gluco-homonojirimycin 3a, 1-deoxy-L-ido-homonojirimycin 3b, and indolizidine alkaloids 1-deoxy-castanospermine 5a and 1-deoxy-8a-epi-castanospermine 5b, has been achieved. The key step involved is the intermolecular Michael addition of benzylamine to alpha,beta-unsaturated ester 1, derived from D-glucose, which afforded diastereomeric mixture of beta-amino esters 6a and 6b with D-gluco- and L-ido- configuration at C5, respectively. Attempts were made to increase and/or alter the diastereoselectivity at the newly generated stereocenter. The high stereoselectivity, in favor of L-ido-isomer 6b, was achieved under kinetically controlled conditions by using lithium N-benzyl amide as a Michael donor. The beta-amino esters 6a and 6b represent common intermediates to target molecules. Thus, LAH reduction of 6a and 6b, individually, gave beta-amino alcohol 7a and 7b. Sequential hydrogenolysis, selective protection of the amino group, followed by hydrolysis of the 1,2-acetonide functionality, and hydrogenation gave 3a and 3b, respectively. On the other hand, the beta-amino ester 6a was converted to gamma-amino ester 13a by Arndt-Eistert synthesis, which on hydrogenolysis and treatment with sodium acetate gave gamma-lactam 14a. The LAH reduction afforded pyrrolidene. The N-protection-hydrolysis-hydrogenation cascade successfully executed, and 1-deoxy-castanospermine 5a was obtained in good yield. The same sequence of reactions was applied to beta-amino ester 6b, which afforded 1-deoxy-8a-epi-castanospermine 5b.

Research paper thumbnail of An efficient route to thioglycosides with the 2,3-anhydro-D-ribo stereochemistry

An improved route for the synthesis of p-tolyl 2,3-anhydro-5-O-benzoyl-1-thio-beta-D-ribofuranosi... more An improved route for the synthesis of p-tolyl 2,3-anhydro-5-O-benzoyl-1-thio-beta-D-ribofuranoside and its alpha anomer, which are important intermediates in the synthesis of alpha- and beta-D-arabinofuranosides, has been developed. The products are obtained in six steps from D-xylose in 39% overall yield.

Research paper thumbnail of Isolation, characterization, and plasmid pUPI126-mediated indole-3-acetic acid production in acinetobacter strains from rhizosphere of wheat

Applied biochemistry and biotechnology

Thirty-seven strains of Acinetobacter isolated and characterized from rhizosphere of wheat were s... more Thirty-seven strains of Acinetobacter isolated and characterized from rhizosphere of wheat were screened for indole-3-acetic acid (IAA) production. Only eight Acinetobacter strains showed IAA production. The genus Acinetobacter was confirmed by chromosomal DNA transformation assay. Biotyping of eight strains was carried out and they were found to be genospecies of A. junii, A. baumannii, A. genospecies 3, and A. haemolyticus. Five of eight strains produced IAA at the early stationary phase: A. haemolyticus (A19), A. baumannii (A18, A16, A13), and Acinetobactergenospecies 3 (A15). A. junii A6 showed maximum IAA production at log phase and A. genospecies 3 and A. baumannii (A28, A30) at late stationary phase. IAA was extracted by ethyl acetate and purified by preparative thin-layer chromatography. Purified IAA was confirmed by 1H-nuclear magnetic resonance and infrared spectrum analysis. Pot experiments showed a significant increase in plant growth inoculated with eight Acinetobacter ...

Research paper thumbnail of Plasmid encoding IAA and a method thereof

Research paper thumbnail of ChemInform Abstract: Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones

Cheminform, 2010

Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones.-The ti... more Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones.-The title reaction [cf. conditions A)] affords furanuronates of type (V) and (X). Hydrolysis of derivative (Va) followed by Wittig olefination affords the unsaturated ester (VII) as the C1-C6 title synthon.

Research paper thumbnail of ChemInform Abstract: Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones

ChemInform, 2000

Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones.-The ti... more Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones.-The title reaction [cf. conditions A)] affords furanuronates of type (V) and (X). Hydrolysis of derivative (Va) followed by Wittig olefination affords the unsaturated ester (VII) as the C1-C6 title synthon.

Research paper thumbnail of An expeditious synthesis of a (3S,4S,5R)-trihydroxyazepane

Tetrahedron Letters, 2003

Multi-membered N-heterocycles Multi-membered N-heterocycles R 0690 An Expeditious Synthesis of a ... more Multi-membered N-heterocycles Multi-membered N-heterocycles R 0690 An Expeditious Synthesis of a (3S,4S,5R)-Trihydroxyazepane.-Starting from the optically active (I) derived from D-glucose a practical synthesis for the title compound (VIII) is presented. This approach is also useful on a multigram scale.-(DHAVALE*,

Research paper thumbnail of A short and efficient synthesis of 1-deoxy-castanospermine and 1-deoxy-8a-epi-castanospermine

Tetrahedron Letters, 2001

A new route for the synthesis of 1-deoxy-castanospermine 2 and 1-deoxy-8a-epi-castanospermine 3 h... more A new route for the synthesis of 1-deoxy-castanospermine 2 and 1-deoxy-8a-epi-castanospermine 3 has been developed via a sequential triple reductive amination process of a suitably protected d-gluco-oct-5-ulo-1,8-dialdose, which was easily prepared by three carbon homologation of readily available α-d-xylo-pentodialdose using an appropriate Grignard reagent followed by oxidation.

Research paper thumbnail of Concise and practical synthesis of (2S,3R,4R,5R) and (2S,3R,4R,5S)-1,6-dideoxy-1,6-iminosugars

Tetrahedron, 2003

The syntheses of (2S,3R,4R,5R) and (2S,3R,4R,5S)-1,6-dideoxy-1,6 iminosugars 1a and 1b, respectiv... more The syntheses of (2S,3R,4R,5R) and (2S,3R,4R,5S)-1,6-dideoxy-1,6 iminosugars 1a and 1b, respectively, from d-glucose are described. The key transformations in this reaction sequence include regio-selective epoxide ring opening with N-benzylamine followed by intramolecular reductive amination of amino-aldehyde.

Research paper thumbnail of Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones

Synthesis, 2000

paper, Synthesis 2000; 2000(3): 395-398 DOI: 10.1055/s-2000-6343. © Georg Thieme Verlag, Rüdigers... more paper, Synthesis 2000; 2000(3): 395-398 DOI: 10.1055/s-2000-6343. © Georg Thieme Verlag, Rüdigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. This journal, including all individual contributions and illustrations published ...

Research paper thumbnail of Intermolecular Michael Addition of Substituted Amines to a Sugar-Derived α,β-Unsaturated Ester:  Synthesis of 1-Deoxy- d - g luco - and - l - i do -homonojirimycin, 1-Deoxy-castanospermine and 1-Deoxy-8a- epi -castanospermine

The Journal of Organic Chemistry, 2001

The synthesis of polyhydroxylated piperidine alkaloids, namely, 1-deoxy-D-gluco-homonojirimycin 3... more The synthesis of polyhydroxylated piperidine alkaloids, namely, 1-deoxy-D-gluco-homonojirimycin 3a, 1-deoxy-L-ido-homonojirimycin 3b, and indolizidine alkaloids 1-deoxy-castanospermine 5a and 1-deoxy-8a-epi-castanospermine 5b, has been achieved. The key step involved is the intermolecular Michael addition of benzylamine to alpha,beta-unsaturated ester 1, derived from D-glucose, which afforded diastereomeric mixture of beta-amino esters 6a and 6b with D-gluco- and L-ido- configuration at C5, respectively. Attempts were made to increase and/or alter the diastereoselectivity at the newly generated stereocenter. The high stereoselectivity, in favor of L-ido-isomer 6b, was achieved under kinetically controlled conditions by using lithium N-benzyl amide as a Michael donor. The beta-amino esters 6a and 6b represent common intermediates to target molecules. Thus, LAH reduction of 6a and 6b, individually, gave beta-amino alcohol 7a and 7b. Sequential hydrogenolysis, selective protection of the amino group, followed by hydrolysis of the 1,2-acetonide functionality, and hydrogenation gave 3a and 3b, respectively. On the other hand, the beta-amino ester 6a was converted to gamma-amino ester 13a by Arndt-Eistert synthesis, which on hydrogenolysis and treatment with sodium acetate gave gamma-lactam 14a. The LAH reduction afforded pyrrolidene. The N-protection-hydrolysis-hydrogenation cascade successfully executed, and 1-deoxy-castanospermine 5a was obtained in good yield. The same sequence of reactions was applied to beta-amino ester 6b, which afforded 1-deoxy-8a-epi-castanospermine 5b.

Research paper thumbnail of An efficient route to thioglycosides with the 2,3-anhydro-d-ribo stereochemistry

Carbohydrate Research, 2004

An improved route for the synthesis of p-tolyl 2,3-anhydro-5-O-benzoyl-1-thio-beta-D-ribofuranosi... more An improved route for the synthesis of p-tolyl 2,3-anhydro-5-O-benzoyl-1-thio-beta-D-ribofuranoside and its alpha anomer, which are important intermediates in the synthesis of alpha- and beta-D-arabinofuranosides, has been developed. The products are obtained in six steps from D-xylose in 39% overall yield.

Research paper thumbnail of Isolation, Characterization, and Plasmid pUPI126-Mediated Indole-3-Acetic Acid Production in Acinetobacter Strains from Rhizosphere of Wheat

Applied Biochemistry and Biotechnology, 2002

Thirty-seven strains of Acinetobacter isolated and characterized from rhizosphere of wheat were s... more Thirty-seven strains of Acinetobacter isolated and characterized from rhizosphere of wheat were screened for indole-3-acetic acid (IAA) production. Only eight Acinetobacter strains showed IAA production. The genus Acinetobacter was confirmed by chromosomal DNA transformation assay. Biotyping of eight strains was carried out and they were found to be genospecies of A. junii, A. baumannii, A. genospecies 3, and A. haemolyticus. Five of eight strains produced IAA at the early stationary phase: A. haemolyticus (A19), A. baumannii (A18, A16, A13), and Acinetobacter genospecies 3 (A15). A. junii A6 showed maximum IAA production at log phase and A. genospecies 3 and A. baumannii (A28, A30) at late stationary phase. IAA was extracted by ethyl acetate and purified by preparative thin-layer chromatography. Purified IAA was confirmed by 1 H-nuclear magnetic resonance and infrared spectrum analysis. Pot experiments showed a significant increase in plant growth inoculated with eight Acinetobacter genospecies as compared to control plants. IAA production was found to be encoded by plasmid pUPI126. All eight strains of Acinetobacter contain a plasmid pUPI126 with a molecular weight of 40 kb. Plasmid pUPI126 was transformed into Escherichia coli HB101 at a frequency of 5 × 10-5 , and E. coli HB101 (pUPI126) transformants also showed IAA activity. PUPI126 also encoded resistance to selenium, tellurium, and lead. This is the first report of plasmid-encoded IAA production in the genus Acinetobacter.

Research paper thumbnail of Synthesis of C 1-C 6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones

Synthesis, 2000

paper, Synthesis 2000; 2000(3): 395-398 DOI: 10.1055/s-2000-6343. © Georg Thieme Verlag, Rüdigers... more paper, Synthesis 2000; 2000(3): 395-398 DOI: 10.1055/s-2000-6343. © Georg Thieme Verlag, Rüdigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. This journal, including all individual contributions and illustrations published ...

Research paper thumbnail of Chiron approaches to polyhydroxylated piperidines: promising glycosidase inhibitors

Arkivoc, Jul 14, 2002

New chiron approaches towards the syntheses of polyhydroxylated piperidine analogues are describe... more New chiron approaches towards the syntheses of polyhydroxylated piperidine analogues are described. The methodologies involve 1,3-addition of methyl magnesium bromide and silyl ketene acetal to D-glucose derived nitrone, intramolecular Michael addition to D-glucose derived α,β-unsaturated ester and double reductive amination of 5-keto aldose as key steps.

Research paper thumbnail of Chiron approaches to glycosidase inhibitor azepanes and c1_c6 segment of carbonolide b_aglycone of carbomycin b

Research paper thumbnail of Plasmid encoding IAA and a method thereof

Research paper thumbnail of An Expeditious Synthesis of a (3S,4S,5R)-Trihydroxyazepane

Tetrahedron Letters, Dec 30, 2003

Multi-membered N-heterocycles Multi-membered N-heterocycles R 0690 An Expeditious Synthesis of a ... more Multi-membered N-heterocycles Multi-membered N-heterocycles R 0690 An Expeditious Synthesis of a (3S,4S,5R)-Trihydroxyazepane.-Starting from the optically active (I) derived from D-glucose a practical synthesis for the title compound (VIII) is presented. This approach is also useful on a multigram scale.-(DHAVALE*,

Research paper thumbnail of Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar a-Diazo Ketones

Synthesis Stuttgart, 2000

paper, Synthesis 2000; 2000(3): 395-398 DOI: 10.1055/s-2000-6343. © Georg Thieme Verlag, Rüdigers... more paper, Synthesis 2000; 2000(3): 395-398 DOI: 10.1055/s-2000-6343. © Georg Thieme Verlag, Rüdigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. This journal, including all individual contributions and illustrations published ...

Research paper thumbnail of A short and efficient synthesis of 1-deoxy-castanospermine and 1-deoxy-8a- epi-castanospermine

Tetrahedron Letters, Jan 22, 2001

A new route for the synthesis of 1-deoxy-castanospermine 2 and 1-deoxy-8a-epi-castanospermine 3 h... more A new route for the synthesis of 1-deoxy-castanospermine 2 and 1-deoxy-8a-epi-castanospermine 3 has been developed via a sequential triple reductive amination process of a suitably protected d-gluco-oct-5-ulo-1,8-dialdose, which was easily prepared by three carbon homologation of readily available α-d-xylo-pentodialdose using an appropriate Grignard reagent followed by oxidation.

Research paper thumbnail of Intermolecular Michael Addition of Substituted Amines to a Sugar-Derived α,β-Unsaturated Ester: Synthesis of 1-Deoxy- d - g luco - and - l - i do -homonojirimycin, 1-Deoxy-castanospermine and 1-Deoxy-8a- epi -castanospermine

The Journal of Organic Chemistry, Feb 1, 2001

The synthesis of polyhydroxylated piperidine alkaloids, namely, 1-deoxy-D-gluco-homonojirimycin 3... more The synthesis of polyhydroxylated piperidine alkaloids, namely, 1-deoxy-D-gluco-homonojirimycin 3a, 1-deoxy-L-ido-homonojirimycin 3b, and indolizidine alkaloids 1-deoxy-castanospermine 5a and 1-deoxy-8a-epi-castanospermine 5b, has been achieved. The key step involved is the intermolecular Michael addition of benzylamine to alpha,beta-unsaturated ester 1, derived from D-glucose, which afforded diastereomeric mixture of beta-amino esters 6a and 6b with D-gluco- and L-ido- configuration at C5, respectively. Attempts were made to increase and/or alter the diastereoselectivity at the newly generated stereocenter. The high stereoselectivity, in favor of L-ido-isomer 6b, was achieved under kinetically controlled conditions by using lithium N-benzyl amide as a Michael donor. The beta-amino esters 6a and 6b represent common intermediates to target molecules. Thus, LAH reduction of 6a and 6b, individually, gave beta-amino alcohol 7a and 7b. Sequential hydrogenolysis, selective protection of the amino group, followed by hydrolysis of the 1,2-acetonide functionality, and hydrogenation gave 3a and 3b, respectively. On the other hand, the beta-amino ester 6a was converted to gamma-amino ester 13a by Arndt-Eistert synthesis, which on hydrogenolysis and treatment with sodium acetate gave gamma-lactam 14a. The LAH reduction afforded pyrrolidene. The N-protection-hydrolysis-hydrogenation cascade successfully executed, and 1-deoxy-castanospermine 5a was obtained in good yield. The same sequence of reactions was applied to beta-amino ester 6b, which afforded 1-deoxy-8a-epi-castanospermine 5b.

Research paper thumbnail of An efficient route to thioglycosides with the 2,3-anhydro-D-ribo stereochemistry

An improved route for the synthesis of p-tolyl 2,3-anhydro-5-O-benzoyl-1-thio-beta-D-ribofuranosi... more An improved route for the synthesis of p-tolyl 2,3-anhydro-5-O-benzoyl-1-thio-beta-D-ribofuranoside and its alpha anomer, which are important intermediates in the synthesis of alpha- and beta-D-arabinofuranosides, has been developed. The products are obtained in six steps from D-xylose in 39% overall yield.

Research paper thumbnail of Isolation, characterization, and plasmid pUPI126-mediated indole-3-acetic acid production in acinetobacter strains from rhizosphere of wheat

Applied biochemistry and biotechnology

Thirty-seven strains of Acinetobacter isolated and characterized from rhizosphere of wheat were s... more Thirty-seven strains of Acinetobacter isolated and characterized from rhizosphere of wheat were screened for indole-3-acetic acid (IAA) production. Only eight Acinetobacter strains showed IAA production. The genus Acinetobacter was confirmed by chromosomal DNA transformation assay. Biotyping of eight strains was carried out and they were found to be genospecies of A. junii, A. baumannii, A. genospecies 3, and A. haemolyticus. Five of eight strains produced IAA at the early stationary phase: A. haemolyticus (A19), A. baumannii (A18, A16, A13), and Acinetobactergenospecies 3 (A15). A. junii A6 showed maximum IAA production at log phase and A. genospecies 3 and A. baumannii (A28, A30) at late stationary phase. IAA was extracted by ethyl acetate and purified by preparative thin-layer chromatography. Purified IAA was confirmed by 1H-nuclear magnetic resonance and infrared spectrum analysis. Pot experiments showed a significant increase in plant growth inoculated with eight Acinetobacter ...

Research paper thumbnail of Plasmid encoding IAA and a method thereof

Research paper thumbnail of ChemInform Abstract: Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones

Cheminform, 2010

Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones.-The ti... more Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones.-The title reaction [cf. conditions A)] affords furanuronates of type (V) and (X). Hydrolysis of derivative (Va) followed by Wittig olefination affords the unsaturated ester (VII) as the C1-C6 title synthon.

Research paper thumbnail of ChemInform Abstract: Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones

ChemInform, 2000

Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones.-The ti... more Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones.-The title reaction [cf. conditions A)] affords furanuronates of type (V) and (X). Hydrolysis of derivative (Va) followed by Wittig olefination affords the unsaturated ester (VII) as the C1-C6 title synthon.

Research paper thumbnail of An expeditious synthesis of a (3S,4S,5R)-trihydroxyazepane

Tetrahedron Letters, 2003

Multi-membered N-heterocycles Multi-membered N-heterocycles R 0690 An Expeditious Synthesis of a ... more Multi-membered N-heterocycles Multi-membered N-heterocycles R 0690 An Expeditious Synthesis of a (3S,4S,5R)-Trihydroxyazepane.-Starting from the optically active (I) derived from D-glucose a practical synthesis for the title compound (VIII) is presented. This approach is also useful on a multigram scale.-(DHAVALE*,

Research paper thumbnail of A short and efficient synthesis of 1-deoxy-castanospermine and 1-deoxy-8a-epi-castanospermine

Tetrahedron Letters, 2001

A new route for the synthesis of 1-deoxy-castanospermine 2 and 1-deoxy-8a-epi-castanospermine 3 h... more A new route for the synthesis of 1-deoxy-castanospermine 2 and 1-deoxy-8a-epi-castanospermine 3 has been developed via a sequential triple reductive amination process of a suitably protected d-gluco-oct-5-ulo-1,8-dialdose, which was easily prepared by three carbon homologation of readily available α-d-xylo-pentodialdose using an appropriate Grignard reagent followed by oxidation.

Research paper thumbnail of Concise and practical synthesis of (2S,3R,4R,5R) and (2S,3R,4R,5S)-1,6-dideoxy-1,6-iminosugars

Tetrahedron, 2003

The syntheses of (2S,3R,4R,5R) and (2S,3R,4R,5S)-1,6-dideoxy-1,6 iminosugars 1a and 1b, respectiv... more The syntheses of (2S,3R,4R,5R) and (2S,3R,4R,5S)-1,6-dideoxy-1,6 iminosugars 1a and 1b, respectively, from d-glucose are described. The key transformations in this reaction sequence include regio-selective epoxide ring opening with N-benzylamine followed by intramolecular reductive amination of amino-aldehyde.

Research paper thumbnail of Synthesis of C1-C6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones

Synthesis, 2000

paper, Synthesis 2000; 2000(3): 395-398 DOI: 10.1055/s-2000-6343. © Georg Thieme Verlag, Rüdigers... more paper, Synthesis 2000; 2000(3): 395-398 DOI: 10.1055/s-2000-6343. © Georg Thieme Verlag, Rüdigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. This journal, including all individual contributions and illustrations published ...

Research paper thumbnail of Intermolecular Michael Addition of Substituted Amines to a Sugar-Derived α,β-Unsaturated Ester:  Synthesis of 1-Deoxy- d - g luco - and - l - i do -homonojirimycin, 1-Deoxy-castanospermine and 1-Deoxy-8a- epi -castanospermine

The Journal of Organic Chemistry, 2001

The synthesis of polyhydroxylated piperidine alkaloids, namely, 1-deoxy-D-gluco-homonojirimycin 3... more The synthesis of polyhydroxylated piperidine alkaloids, namely, 1-deoxy-D-gluco-homonojirimycin 3a, 1-deoxy-L-ido-homonojirimycin 3b, and indolizidine alkaloids 1-deoxy-castanospermine 5a and 1-deoxy-8a-epi-castanospermine 5b, has been achieved. The key step involved is the intermolecular Michael addition of benzylamine to alpha,beta-unsaturated ester 1, derived from D-glucose, which afforded diastereomeric mixture of beta-amino esters 6a and 6b with D-gluco- and L-ido- configuration at C5, respectively. Attempts were made to increase and/or alter the diastereoselectivity at the newly generated stereocenter. The high stereoselectivity, in favor of L-ido-isomer 6b, was achieved under kinetically controlled conditions by using lithium N-benzyl amide as a Michael donor. The beta-amino esters 6a and 6b represent common intermediates to target molecules. Thus, LAH reduction of 6a and 6b, individually, gave beta-amino alcohol 7a and 7b. Sequential hydrogenolysis, selective protection of the amino group, followed by hydrolysis of the 1,2-acetonide functionality, and hydrogenation gave 3a and 3b, respectively. On the other hand, the beta-amino ester 6a was converted to gamma-amino ester 13a by Arndt-Eistert synthesis, which on hydrogenolysis and treatment with sodium acetate gave gamma-lactam 14a. The LAH reduction afforded pyrrolidene. The N-protection-hydrolysis-hydrogenation cascade successfully executed, and 1-deoxy-castanospermine 5a was obtained in good yield. The same sequence of reactions was applied to beta-amino ester 6b, which afforded 1-deoxy-8a-epi-castanospermine 5b.

Research paper thumbnail of An efficient route to thioglycosides with the 2,3-anhydro-d-ribo stereochemistry

Carbohydrate Research, 2004

An improved route for the synthesis of p-tolyl 2,3-anhydro-5-O-benzoyl-1-thio-beta-D-ribofuranosi... more An improved route for the synthesis of p-tolyl 2,3-anhydro-5-O-benzoyl-1-thio-beta-D-ribofuranoside and its alpha anomer, which are important intermediates in the synthesis of alpha- and beta-D-arabinofuranosides, has been developed. The products are obtained in six steps from D-xylose in 39% overall yield.

Research paper thumbnail of Isolation, Characterization, and Plasmid pUPI126-Mediated Indole-3-Acetic Acid Production in Acinetobacter Strains from Rhizosphere of Wheat

Applied Biochemistry and Biotechnology, 2002

Thirty-seven strains of Acinetobacter isolated and characterized from rhizosphere of wheat were s... more Thirty-seven strains of Acinetobacter isolated and characterized from rhizosphere of wheat were screened for indole-3-acetic acid (IAA) production. Only eight Acinetobacter strains showed IAA production. The genus Acinetobacter was confirmed by chromosomal DNA transformation assay. Biotyping of eight strains was carried out and they were found to be genospecies of A. junii, A. baumannii, A. genospecies 3, and A. haemolyticus. Five of eight strains produced IAA at the early stationary phase: A. haemolyticus (A19), A. baumannii (A18, A16, A13), and Acinetobacter genospecies 3 (A15). A. junii A6 showed maximum IAA production at log phase and A. genospecies 3 and A. baumannii (A28, A30) at late stationary phase. IAA was extracted by ethyl acetate and purified by preparative thin-layer chromatography. Purified IAA was confirmed by 1 H-nuclear magnetic resonance and infrared spectrum analysis. Pot experiments showed a significant increase in plant growth inoculated with eight Acinetobacter genospecies as compared to control plants. IAA production was found to be encoded by plasmid pUPI126. All eight strains of Acinetobacter contain a plasmid pUPI126 with a molecular weight of 40 kb. Plasmid pUPI126 was transformed into Escherichia coli HB101 at a frequency of 5 × 10-5 , and E. coli HB101 (pUPI126) transformants also showed IAA activity. PUPI126 also encoded resistance to selenium, tellurium, and lead. This is the first report of plasmid-encoded IAA production in the genus Acinetobacter.

Research paper thumbnail of Synthesis of C 1-C 6 Segment of Carbonolide B: Wolff Rearrangement of Sugar α-Diazo Ketones

Synthesis, 2000

paper, Synthesis 2000; 2000(3): 395-398 DOI: 10.1055/s-2000-6343. © Georg Thieme Verlag, Rüdigers... more paper, Synthesis 2000; 2000(3): 395-398 DOI: 10.1055/s-2000-6343. © Georg Thieme Verlag, Rüdigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. This journal, including all individual contributions and illustrations published ...